This invention relates to improved cutting tools useful for cutting slots in workpieces and is more particularly concerned with improved cutting tools for gear cutting applications.
It is known in the art of gear cutting to provide for cutting tools which can be easily resharpened by their users by simply regrinding a profile on a cutting end of each tool. The cutting face of such a tool does not require resharpening, and this permits a preservation of the cutting face for metallurgical of other types of treatments which improve cutting and wear characteristics of the tool. In addition, it is known to provide in cutting tools of this type a built-in side rake angle of the cutting face relative to the orientation of such tools in radial slots in cutterheads designed to carry a plurality of tools for gear cutting purposes. Built-in rake angles are disclosed, for example, in U.S. Pat. No. 4,060,881 (commonly owned herewith), and the descriptions of that patent are incorporated herein by reference to the extent necessary to provide additional background information regarding the design and usage of certain cutting tools in bevel gear cutting applications. Similar type tools can be used in spur and helical gear cutting applications in which the tools are mounted in a carrier for being brought into engagement with a cylindrical workpiece for forming spur or helical gears.
However, it has been found that there is a problem of obtaining desired tool geometry for certain required side rake angles that are needed for cutting different degrees of softness of workpiece material. When cutting a workpiece formed from a softer steel than is conventionally used, it is desirable to provide a greater side rake angle on the cutting faces of the tools operating on such a workpiece. As shown and described in U.S. Pat. No. 4,060,881, the side rake angle of certain forms of tooling can be included thereon by simply grinding a prefered angle on the face of the tool at the time of its original manufacture. Thereafter, the tool is periodically resharpened without regrinding the cutting face portion thereof. A single and preferred side rake angle for any given tool satisfies many cutting applications, however, side rake angles which are substantially greater than those normally used result in a significant and unwanted reduction in thickness of the tool along one side of the tool blank.
In accordance with the present invention, the cutting faces of tools are provided with compound side rake angles which serve to maintain desired tool thickness while at the same time providing the requisite geometry for cutting certain types of materials. The compound rake angles which are provided comprise two or more planar surfaces formed along the length of the cutting face of the tool, and these surfaces are related to one another in specific ways which provide for improved cutting action, better tool strength, and, in some cases, better control of chip formation and removal of chips from the tooth slot being formed.
The planar surfaces which are formed on the tools of this invention do not require resharpening at the time the tool is resharpened, and this permits the use of metallurgical or coating treatments on such surfaces for improving tool life and cutting action. In addition, the surfaces can be formed very easily on tools at the time of original manufacture without a requirement for highly sophisticated equipment for such manufacture.
In accordance with a specific embodiment of the present invention, a gear cutting tool is provided with a cutting face having a compound side rake angle formed in the tool for all or part of the length of the tool. The compound side rake angle may consist of two adjacent planar surfaces which intersect in a line parallel to a longitudinal axis of the tool, and the axis of intersection may, in certain specific applications, be positioned so as to not intersect any portion of the cutting edge of the tool. In other applications the axis of intersection may fall across a portion of the tool cutting edge.
These and other features and advantages of the present invention will become apparent in the more detailed discussion which follows, and in that discussion reference will be made to the accompanying drawings as briefly described below.